Sensing of a user's physiological context may provide continuous information about the user's biological and mental state, behavior and preferences so long as the user is using the device for other everyday needs. This information may be used by context-aware applications for personalization related to a user's state of health, such as coaching, alerting, chronic disease management, personalized medicine, and the like. Today's proliferation of wearable computing/communication devices may provide opportunity for sensing of a user's physiological context. However, determination of the user's physiological context may consume a substantial amount of the user's time and effort and may require using substantial energy, hardware, and computing resources. For example, measurements of a user's sweat rate may require the use of special equipment, may have to be performed in special conditions (e.g., in a laboratory), and may not always be performed in real-time, opportunistic or continuous fashion.